In the development of sofas which are convertible into beds, hereinafter referred to as convertible sofas, it has become conventional to utilize a folding mattress frame formed of a plurality of spring sections which can be folded up into a sofa position and stored in the seat beneath the seat cushions of the sofa, or can be selectively unfolded into a bed position. to effect conversion of such a sofa to a bed, the mattress frame is lifted out of the storage position beneath the seat and one of the spring sections unfolded forwardly of the sofa into the room. In the closed position, the mattress frame generally forms the base for the seat cushions of the sofa.
In an effort to maximize comfort of the sofa when in the bed position, it has become the practice to use rather large and bulky mattresses that remain with the spring section in the closed position. Such an arrangement requires a relatively large front board, or else the sofa must be upholstered and include a skirt all the way to the floor to hide the mattress and frame behind the front section. It is apparent that in such an arrangement, the design possibilities are severely limited, and a "high leg" design, convertible sofa has not been possible.
Moreover, conventional convertible sofas take up a considerable amount of floor space in a room in the open or bed position, on the order of 2-3 times the space taken up by the couch alone. The reason for the large amount of floor space is that the mattress frame folds out of the sofa to move clear of the rear upholstered back cushions which remain with the couch. With the added weight of the mattress and several linkages and springs, the mattress frame is heavy and difficult to convert from one position to the other.